A gradient-corrected density functional study of structure, harmonic vibrational frequencies and charge distribution of benzenesulfonate anion on theground-state potential energy surface

A density functional study of the structure, harmonic vibrational force fie ld, and charge distribution of benzenesulfonate anion combined with a solid -state FT-IR study of sodium benzenesulfonate is presented. Two combination s of exchange/correlation functionals (BLYP and B3LYP) were employed within the quantum chemical approach, using the standard double-zeta quality 6-31 +G(d) basis set for orbital expansion. The DFT predicted structure of the s tudied species is in a very good agreement with the available crystallograp hic data (significantly better in comparison with our previous HF SCF resul ts for benzenesulfonate and 4-methylbenzenesulfonate anions). Both the B3LY P and BLYP/6-31 + G(d) vibrational analyses of the benzenesulfonate anion c onfirmed our previously proposed reassignments of several vibrational bands of this system based on the HF SCF/6-31 + G(d) vibrational force field. Th e B3LYP predicted vibrational frequencies are superior to the BLYP ones. Th e Mulliken population analysis predicts a strong anionic charge delocalizat ion over the phenyl ring (-0.54 and -0.56e, B3LYP and BLYP levels correspon dingly), whereas according to the electrostatic potential derived schemes, it is mainly localized within the SO3 group. The latter result seems to be more in line both with the observed hydrogen bonding in the solid crystalli ne hydrates and with chemical intuition. (C) 2000 Elsevier Science B.V. All rights reserved.